Purchase this article with an account.
Sara Padroni, Georgia Toliou, Ioannis A. Aslanides; Long Term Variation In Corneal Thickness In Keratoconic Eyes Treated With Prk And Cross Linking. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5740.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To show the accuracy of ablation depth, variation and long term stability of the cornea thickness in 14 keratoconic eyes treated with photorefractive keratectomy (PRK) and Collagen Cross Linking (CXL). The measurements were taken with the Artemis High Frequency Ultrasound Scanner pre operatively, at 3 and 12 months after surgery.
This prospective pilot study included 14 eyes undergoing PRK and CXL with a mean pre operative spherical equivalent of -5.47D. All patients underwent pre and post-operative measurements of best correected visual acuity (BCVA), refraction corneal topography and slit lamp examination. After treatment with excimer laser all patients underwent CXL treatment according to a standard protocol. Epithelial thickness variation, stromal thickness and residual stromal bed were measured before and after PRK and CXL.
The mean age of the patients at surgery was 30.44 (SD 10.5) years. Pre operative BCVA was 0.6 (SD 0.29), 0.65 (SD 0.29) at 3 months and 0.71 (SD 0.31) at 1 year. The estimated mean ablation depth was 39.18 microns (SD 17.40). The actual mean ablation at 12 months was 40.83 microns (SD 20.00). The minimum corneal thickness (including epithelium) was 473 microns pre operatively (SD 48.84), it was 422 (SD 41.39) at 3 months and at 12 months it was 431 (SD 36.56). The mean corneal peripheral thickness was 533 microns (SD 31.44) pre operatively, 498 (SD 27.21) at 3 months and 505 (SD 25.84) at 12 months. The central corneal thickness in the area 0-3 mm followed a similar trend with values of 490 microns (SD 34.14) pre-op, 443 (SD 42.31) at 3 months and 453 (SD 31.33) at 12 months postoperatively.
Following CXL and PRK, the corneal thickness has a bimodal recovery pattern. After an initial decrease due to the excimer laser treatment an overall increase across all the areas of the corneal stroma is observed. Furthermore the increase in residual stromal bed after CXL is observed and maintained over a period of 12 months. The precision and accuracy of the high frequency ultrasound scanner confirm that the estimation of ablation depth prior to PRK is accurate. Furthermore, PRK and CXL have a long term effect on both vision and corneal thickness recovery that persists over a period of 12 months, at least.
This PDF is available to Subscribers Only